Method of treating aircraft fabrics and products thereof



Patented Oct. 5, 1943 v MErnon F TREATING AIRCRAFT nannies AND PRODUCTS THEREOF 1 Leo Roon, South Orange, N. J., assignor to Roxalin Flexible Finishes, Inc., Elizabeth, N. 55., a corporation of New Jersey i .No Drawing.

12 Claims.

The object of this invention is t6 protect the doped fabrics of aircraft against deteriorationdue to mildew and fungus growths.

It is the common practice in the manufacture of aircraft to cover the framework of various parts of the structure with fabric, usually linen, to thereupon shrink the fabric by sponging the same with water, in order to render it taut, and to thereafter apply a cellulosic dope to the exposed surface of the fabric.

Experience has shown that those portions of the fabric which cover dead air spaces in e. g., aerofoils, stabilizers, rudders, elevators and ailerons, which are sealed so that their interiors are not susceptible of ready periodical inspection, often mildew badly under the dope finish. It is not uncommon that the mildewing or fungicidal growths so weaken the fabric that only the dope finish serves to hold the parts together. pernicious condition of the fabric is concealed by the exterior finish which appears sound and serviceable while the underlying structure is, in fact, inherently dangerous and liable to failure during flight.

I have discovered that doped aircraft fabrics may be effectually protected against deterioration from the causes stated by the use of a mildew proofing agent, especially copper naphthenate. It was found that copper naphthenate, prepared according to the method of United States Letters Patent No. 2,113,496 of April 5, 1938, was highly suitable for this purpose and I have incorporated it in the fabric in two distinct ways.

According to the first method, I prepared a copper naphthenate emulsion by compounding the following:

Parts Copper naphthenate (6% metallic copper based-on the total weight of the copper naphthenate) 60 Concentrated ammonium hydroxide 8 Ethylene diamine 10 Water 10 to give equivalent shrinkage and consequent tautness to that of the usual water sponging. It

Application October 24, 1941, Serial No. 416,354

1 was also found to effectually introduce the copper into the fibres of the fabric.

This

After the fabric was dry, there-was applied thereto the conventional clear cellulosic dope,

aluminum dope and top coat enamel to form the usual waterproofing coating.

Treatments of the foregoing method, as stated, were carried out many months ago and at the time of this writing no sign of mildew or fungus growths have appeared. The thus treated fabric remains as strong and serviceable as when applied to the framework. Comparative samples, prepared at the same time, with the conventional plain water sponging and subsequent clear dope, aluminum dope and top enamel finish and subjected to the same atmospheric conditions, have badly deteriorated during the intervening period.

According to my second copper naphthenate treatment, I prepared a cellulosic dope by compounding the following formula:

Parts Cellulose nitrate (containing 30% alcohol)" 133 Glycol sebacate solids in toluene) l9 Ethyl acetate 142 Butyl acetate 146 Butyl alcohol 55 Aromatic petroleum naphtha 246 To this was added l/z% (by weight of the above formula) of a solution of copper naphthenate in toluol containing 6% of copper metal,

so as to incorporate the copper naphthenate directly into the dope.

The resulting dope was sprayed onto aircraft fabric which had been prepared by fastening it to a framework and sponging it with plain water and allowing it to shrink and dry in the usual way before the dope was applied. Under present day practice a small amount of chrome green, ground in castor oil, is commonly incorporated in the first clear dope coating as a guide for spraying. This is, however, not necessary here for the clear dope formula, including the addedcopper naphthenate, has a green color which coincidently acts as a spraying guide and enables the operator to see that the clear coat is uniformly applied.

When the copper naphthenate dope was applied two entirely unforeseen phenomena were noted. In the first place, the penetration of the dope into the fibres of the fabric was materially increased over that of the same dope free of copper naphthenate content. This is highly desirable and a, much sought for advantage. In the second place, the presence of the copper naphthenate seemed to produce a better sealing coat on the fabric, so that the same number and same thickness of sealing coats, the final finish was smoother.

Instead of using a nitrocellulose dope and incorporating the copper naphthenate therein as described, I may employ other forms of dope such, e. g., as a cellulose acetate butyrate dope. By way of example, there was prepared a dope in accordance with United States Navy specifications as follows:

Pounds Cellulose acetate butyrate 90 Triphenyl phosphate 10' Diacetone alcohoL 135" Ethyl acetate 315 Toluene 180 Acetone 270 To this dope was added a copper naphthenate solution using toluene as a vehicle. The resulting product was unsatisfactory for the copper dope formulation in such amounts that the quantity of copper present was approximately 2% or 3% by weight, of the solids in the dope. This dope, with the copper naphthenate therein, was applied to the fabric in a quantity to give .625 ozs. of film per square yard, per application, as commonly required by United States Navy specifications. This procedure produced 357% of copper on the fabric or 309% of copper on the basis of the film and fabric. Tests, subsequently carried out on samples of this treatment, were highly satisfactory.

After applying the copper naphthenate dopes, as hereinbefore stated, subsequent coatings of aluminum dope and top coat enamel were superimposed, as in the first example, and the resulting structure was exposed to the influence of mildew, along with comparative samples which had been prepared in the same way, but without including the copper naphthenate. During the period which has since transpired, the said comparative samples have badly deteriorated while the fabric which was treated with the copper naphthenate dop'e continues to retain its original condition and strength.

The discoveries hereinbefore described are of much practical importance for thereby a pernicious source of aircraft failure, with all-too-frequent loss of life to trained fiyers and technicians, is eliminated and safety is assured through the exclusion of the causes stated.

It is to be also noted that the employment of this invention does not entail any additional mechanical operation to the conventional method of aircraft finishing, nor is training in any special technique required of the workmen who ordinarily fabricate and finish the fabric thereof. In the water-copper naphthenate treatment, the copper naphthenate is merely added to the sponging water and said water is thereafter applied in the same way as heretofore. According to the copper naphthenate dope treatment, the copper naphthenate solution is simply added to the dope, as during the course of manufacture thereof, and thereafter the spraying operator ap plies such modified dope in the same old way, but without the necessity of adding chrome green, ground in castor oil, as a color guide.

I have referred to clear dope in theforegoing explanation, but it is to be noted that the copper naphthenate may also be added to colored dopes as well, these being used particularly where separate superimposed color coatings are to be omitted.

The tests carried out in my research with respect to this invention, showed that copper naphthenate produced the best results as an airfract fabric mildewproofing agent. Alternates, but not -so satisfactory, are mercury naphthenate, copper or mercury resinates, zinc naphthenate, phenol mercury oleate, tolyl mercury salicylate and certain fungicides which are compatible with the particular dope formulation to be employed.

The foregoing description sets forth two illustrative ways of accomplishing the object of this invention, but the invention is to be understood as fully commensurate with the appended claims.

Having thus fully described the invention, what I claim as new and desire to secure by Letters Patent is: I

1. The method which comprises, attaching a textile fabric to a structural framework of an aircraft, thereafter applying a shrinking agent to the fabric and allowing the fabric to shrink and dry, thereafter applying a sealing agent to the exposed surface of the shrunk fabric, and adding a mildew-proofing composition to one of said agents prior to the application of such agent to the fabric so that the mildew-proofing composition is applied conjointlytherewith.

2. The method which comprises, attaching a f textile fabric to a structural framework of an aircraft, thereafter applying a shrinking agent to the fabric and allowing the fabric to shrink and dry, thereafter applying a cellulosic doping agent to the exposed surface of the shrunk fabric, and adding a mildew-proofing composition to one of said agents prior to the application of such agent to the fabric, so that the mildew-proofing composition is applied conjointly therewith.

3. The method which comprises, attaching a textile fabric to a structural framework of an aircraft, thereafter applying a shrinkin agent to the fabric and allowing the fabric t shrink and dry, thereafter applying a cellulose acetate butyrate doping agent to the exposed surface of the shrunkfabric, and adding a mildew-proof.- ing composition to one of said agents prior to the application of such agent to the fabric, so that the mildew-proofing composition is applied conjointly therewith.

4. The method which comprises, attaching a textile fabric to a structural framework of an aircraft, thereafter applying water and a mildewproofing agent to the fabricjto shrink said i bric, and, after the fabric has shrunk and drie applying a protective coating to the exposed surface of the fabric.

5. The method which comprises, attaching a textile fabric to a structural framework of an aircraft, thereafter shrinking said fabric,"and applying to the exposed surface of the shrunk fabric a protective coating containing a mildew-proofing agent.

6. The method which comprises, attaching a textile fabric to a structural framework of an aircraft, thereafter shrinking said fabric, and applying to the exposed surface of the shrunk fab- 10. An aircraft part comprising a structural ric a coatingof cellulosic dope containing a frame-work of an aircraft, and a shrunk-taut mildew-proofing agent.

'7. The method which comprises, attaching a textile fabric to a structural framework of an aircraft, thereafter shrinking said fabric, and applying to the exposed surface of the shrunk fabric a coating of a cellulose acetate butyrate dope containing a mildew-proofing agent.

8. The method which comprises, attaching a textile fabric to a structural framework of an aircraft, thereafter shrinking said fabric, and applying to the exposed surface of the shrunk fabric a coating of a cellulose acetate butyrate dope containing a copper salt.

fabric being impregnated with cellulose acetate butyrate dope containing a mildew-proofing agent.

LEO ROON. 

